CONCORD, N.H. (CBS) – A former teacher at an elite prep school in New Hampshire who previously left the school under “questionable circumstances” is facing charges of witness tampering and perjury.

The New Hampshire attorney general’s office began an investigation at St. Paul’s School in July 2017 after a report of sexual assaults by teachers on their students and as a result of the ritual known as the “senior salute” that came to light during the high-profile trial of Owen Labrie.

READ MORE: Fall River Convenience Store Owner Shot Dead; Homicide Investigation Underway

During the investigation, authorities learned of a relationship between David Pook, 47, of Warner, N.H. and a former female student.

Pook taught for eight years at St. Paul’s School before investigators say he left under “questionable circumstances” in 2008. He has been employed at the Derryfield School in Manchester since 2009.

The female and Pook were each called before a grand jury.

READ MORE: 'Best Small Cities In America': 8 Massachusetts Communities Make The Top 20 List

A statement from St. Paul’s School detailed that the school “separated from Mr. Pook after he violated school rules governing boundaries between faculty and students. The school found no evidence of a sexual relationship between Mr. Pook and a student.”

Michael Hirschfeld, the current Rector of St. Paul’s School, also said, “”The school leadership at the time should never have given Mr. Pook a recommendation and the fact that it did not inform Derryfield of Mr. Pook’s boundary issues was a failure for which we apologize.”

Pook was subsequently arrested and charged with two counts of witness tampering and two counts of conspiracy to commit perjury.

MORE NEWS: Supply Chain Issues: 'There Really Are Problems Everywhere,' Even For Small Companies

He is scheduled to be arraigned in Merrimack County Superior Court on March 15.